Electrical connector means for coaxial cables and the like



Dec. Z7, 1966 K. KRAUS TRICAL GONNE AXIAL CABLES Fil ELEC CTOR MEANS FOR CO AND THE LIKE ed Aug. 5, 1964 wm Nm m @v E f A A A om @v INV/W15 h w ...l|

INVENTOR.

K A R L KRAUS ATTORNEYS 3,295,095 ELECTRICAL CONNECTOR MEANS FOR COAXIAL CABLES AND THE LIKE Karl Kraus, Sidney, NSY., assigner to The Bendix Corporation, Sidney, NX., a corporation of Delaware Filed Ang. 3, 1964, Ser. No. 386,931 8 Claims. (Cl. 339-177) This invention relates to electrical equipment and more particularly to means for detachably connecting electrical transmission lines or cables.

An object of the present invention is to provide novel means for electrically and mechanically connecting either rigid or flexible types of cables and particularly coaxial cables of small diameter.

It is also an object of the invention to provide novel mating jacks and plugs for connecting coaxial cables.

Another object of the invention is to provide novel electrical connector means for detachably joining the ends of two coaxial cables in a transmission line without appreciably disturbing the characteristic impedance of the line at the connection.

A further object is to provide novelly constructed connector means for coaxial cables wherein so-called discontinuities -resulting from variations in conductor size are minimized.

In coaxial cable transmission lines including known types of separable connections, conductor discontinuities at the connector create electri-cal disturbances which result in an undesirable increase in the VSWR (voltage standing wave ratio) of the line. The disturbances interfere with the signals transmitted by the line and prevent the eillcient and proper transmission of such signals, particularly in the higher frequency ranges.

It is accordingly another object of the invention to provide a readily separable transmission line wherein the VSWR closely approaches ideal value.

Still another object is to provide novel connector means for coaxial transmission lines wherein conductor-step type discontinuities may be readily compensated to maintain the characteristic impedance of the line and to minimize or eliminate undesirable electrical disturbances resulting from such discontinuities.

A still further object is to provide novelly constructed coaxial electrical connectors which are satisfactory for use in the transmission of electrical energy having a Wide or board range of frequencies, including radio and microwave frequencies.

The invention contemplates a simplified combination of parts of simplified construction which may be mass produced and assembled with facility at low cost to have an exceptionally low VSWR that may be maintained within a narrow range in mass production.

The above and further objects and novel features of the invention will more fully appear from the following detail description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for purposes of illustration only and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

FIG. 1 is a longitudinal or axial sectional view illustrating one form of connector means embodying the invention in coupled relation and assembled with the adjacent ends of two semi-rigid type coaxial cables; and

FIG. 2 is a similar cross sectional view illustrating a modification adapted for connecting the ends of llexible coaxial cables.

The embodiment of the invention shown in FIG. 1, by way of example, comprises a tubular metallic connector or adaptor sleeve 5 which is externally threaded at both United States Patent C ice ends for cooperation with two internally threaded nuts 6. The axial bore or passage through sleeve 5 comprises a central -or mid-portion 8 and enlarged counterbore portions 9 and 10 at the opposite ends thereof for receiving the ends of two coaxial cables 11 which are shown as comprising outer semi-rigid metallic conductors 12 and inner metallic conduct-ors 14 separated Iby insulation 15.

An internal annular ilange 16 is positioned at the inner end of bore portion 8 and serves as a stop for positioning novel socket contact supporting insulating means. As illustrated in FIG. 1, said means consists of two identical oppositely disposed blocks 17 and 18 of suitable insulating material, such as Teilon. Each said block comprises a portion which closely fits bore 8 and a reduced portion `adapted to accurately fit and ll the cylindrical space within ilange 16 so that the end surface ofthe insulating block is substantially llush with the outer transverse surface of the flange. The enlarged portions of blocks 17, 1S tit accurately and are securely held 'between the inner surfaces of flange 16 and a metallic ring 19 which in effect duplicates flange 16 at the opposite end of bore portion S. Ring or flange 19 has a tight press or shrink llt within and engages an annular shoulder at the inner end of counterbore 9 while closely surrounding the reduced end portion of insulating block 18. Ring 19 thus in effect forms a second internal flange in sleeve 5, so that the adaptor thus far described is symmetrical about a central transverse plane. If desired, the flange 16 may be formed by a ring like ring 19.

The insulating blocks 17 and 18 which are thus accurately and securely positioned within sleeve 5 are centrally bored or recessed at their adjacent ends to provide a cylindrical cavity or chamber 20 for a double-ended socket contact 21. The latter is tubular at both ends and is axially or longitudinally slotted in a known manner to provide a plurality of spring lingers 22 to resiliently grip a pin contact. The central portion of contact 21 may be either tubular or solid and the length thereof is preferably just sulllcient to accurately lit into cavity 20. The opposite end portions of the bore through insulating means 17, 18 are of less diameter than cavity 20 for receiving pin contacts or the like to engage with the spring linger sockets at the ends of contact 21. As shown, the pin contacts are formed by the bared end portions of cable inner conductors 14 which have the ends thereof reduced to a cone or bevel shape for facilitating coupling of the cables to the adaptor.

To facilitate coupling the -above described adaptor to each cable 11, a ring tting or tubular ferrule 23 is secured to outer conductor 12, such las soldering at 24. In some installations it may be desirable to employ cooperating screw thread-s in the fitting 23 and on conductor 12 with or without the solder 24, depending upon the degree of moisture tightness and mechanical strength required. The end of each ring 23 adjacent the end of the cable terminates llush with the end yof outer conductor 12 and cable insulation 15 and has a reduced diameter portion which ts closely within the counterbore 9 or 10 at the end of adaptor sleeve 5 into abutting relation with ange 16 or ring 19. A radial external shoulder on ring 23 faces the adjacent end of sleeve 5 and a yieldable sealing gasket 25 is preferably interposed therebetween. The parts are so axially dimensioned that gasket 25 will be somewhat Acompressed when the end of ring 23 abuts flange 16 or 19 in the adaptor.

Nut 6 is coupled to ferrule 23 in any suitable known manner for axial movement therewith and rotation relative thereto, such as by means of a split spring ring 26 which engages oppositely facing grooves in the nut 6 and ferrule 23. Thus, when the nuts 6 are screwed onto the ends of sleeve 5 the cables 11 will be advanced into coupled position as illustrated in FIG. 1 of the drawings.

When thus assembled, the bared ends of inner conductors 14, 14 are coupled by socket contact 21, and the outer conductors 12, 12 are coupled by a composite conductor comprising ferrules 23, and adaptor sleeve 5, including anges 16 and 19.

In the above described embodiment of FIG. 1, the ends of outer conductors 12 of the cables 11 abut anges 16 and 19 which have substantially the same inner diameter as said conductors 12, thus avoiding any change in the characteristic impedance of this portion of the line. However, the socket contact 21 has a larger diameter than inner conductors 14 and hence step-type discontinuities occur at the junctions between inner conductors 14 and the ends of socket contact 21. To maintain constant the re` quired characteristic line impedance across the connector between 'the ends of cables 11, 11, the inner diameter of the outer conductor of the line must be correspondingly increased, according to a known formula, to the diameter of bore 8 around the socket contact or enlarged part of the composite center conductor of the line. For this purpose, the ratio of the outer diameter of the inner conductor to the corresponding inner diameter of the outer conductor in any given assembly may be calculated by well known formulae.

Undesirable electrical disturbances may occur as a result -of these unavoidable steps or discontinuities in the inner and outer conductors of the line within the connector, even though the proper ratio is mait-ained between the outer and inner diameters of the inner and outer conductors, respectively. However, an important advantage of the novel construction contemplated by this invention is that suitable compensation may be readily incorporated in the composite line by introducing short longitudinal sections a of the line between the transverse planes of adjacent steps in the inner and outer conductors, which sections have a characteristic impedance that exceeds the desired characteristic line impedance. These short sections of high impedance function as series inductances which effectively compensate for the capacitative elfects of the line conductor discontinuities.

In the embodiment of FIG. l, it is an easy matter to introduce a compensating section a between each of the transverse planes containing the ends of the Contact cavity 20, which planes also contain the steps in the inner conductors 14, 21 of the line, and one of the transverse planes containing -the inner transverse surfaces of anges 16 and 19 that form the steps in the inner surface of the outer conductors 12, of the line. 'I'he appropriate axial length of each section a for any given transmission line will be dependent on a variety of parameters and may be determined by formula and testing in a manner well known in the art.

In FIG. 2 the invention is shown as being embodied in novel means for connecting the ends of two exible coaxial cables 30 wherein the outer conductors are constituted by braided metal conduits 31 which may in turn be covered by a protective tube 32 of rubber-like, plastic or other suitable insulating material. In this embodiment, the jack or portion most comparable to the adaptor section 5 of FIG. l is premanently att-ached to the end of the left-hand cable 30, as viewed in the drawing. Thus, the tubular end fitting 33 comprises a tapered end portion which is centrally bored to accurately receive the insulated center conductors 34, 35 of the cable and is wedged between the braided outer conductor 31 and insulation 34. A tube 36 has a crimp fit around the overlapped assembly 30, 33 to assist in holding the parts together and insure good electrical contact between conductors 31 and 33.

The central portion of shell or tting 33 has a somewhat larger bore 37 for accurately receiving a tubular insulator 38 which in turn has a central bore 39 to slidably receive a socket contact 40 that is of somewhat 4 ring 19, has a tight fit in a further enlarged bore portion 42 in shell 33. A reduced end portion of insulator 38 lits snugly within ring or flange 41 around the reduced end portion 43 of a pin contact member 43 which projects therethrough into engagement with spring fingers 44 at the adjacent end of contact 40.

The left-hand end of contact 40, as illustrated, has a socket or solder well for receiving cable conductor 35 to which it is preferably soldered or otherwise suitably connected. The connection at this junction is preferably such that when insulation 34 butts insulator 38 the righthand end of contact 40, 44 will engage shoulder 45 in bore 39. To provide compensation for the step or conductor discontinuity at this junction of conductor 35 and contact 40, the end of the latter is secured to the conductor in spaced relation to insulation 34 to provide a short line section b `of high impedance. If desired, a reduced portion of insulation 34 having an axial length b may be retained when baring the end of conductor 35 to iit into bore 39, or a washer having a thickness b may be used. At the opposite end of contact 40 a short cornpensating high impedance line section c may be provided to compensate for the step or discontinuity at the junction of socket 44 and pin contact 43.

A male or plug assembly is mounted on the end of the right-hand cable 30 to interlit or mate with the jack or female assembly above described. The tubular metallic shell or casing member 46 may be secured at one end to a cable 30 in the same manner as shell 33. The other end of said member has a sliding tit in bore 42 and has a central bore 47 to accurately receive a pin contact supporting insulator 48 as an enlarged extensi-on of the cable insulation 34. In the interest of maintaining constant characteristic line impedance, bore 47 is preferably the same diameter as bore 37 in shell 33, and the bore through insulator 48 for receiving an enlarged portion of pin contact 43 is preferably the same diameter as bore portion 39 in insulator 38. The enlarged portion of contact member 43 is hollow and is soldered or otherwise suitably secured to the bared end of cable conductor 35. Pin contact 43, 43' is thus an extension and hence a part of the inner conductor of the cable. Insulator 48 may be installed in bore 47 after pin contact 43 is attached to conductor 35 and may be secured in shell 46 in any suitable manner, such as by slightly indenting the wall of the shell, as at 49, in one or more places.

The enlarged portion of contact member 43 within insulator 48 may be somewhat shorter than the insulator and secured to conductor 35 so as to be centrally disposed longitudinally of the insulator to thereby provide short compensating sections d adjacent the steps in the inner conductor at the ends of said enlarged portions of contact member 43. If desired, reduced portions of insulation 34 and 38 having a length d may extend into the bore of insulator 48 or the spaces in the ends of said bore may be iilled with insulating washers. The reduced end portion 43 Iof pin contact member 43 may have the same diameter as conductors 35, in which event the inner diameter of ring or flange 41 may be the same as the inner diameter of shells 33 and 46 around cable insulation 34.

The assembled connector halves thus attached to cables 30 may be secured together in interiitting coupled relation as illustrated in the drawing by any suitable known vmeans, such as by a nut 50 having threaded engagement with shell 33. The nut may be operably connected with shell member 46 by a split springring 51 in registering grooves in said nut and shell member. A compressible sealing gasket 52 may be interposed between a radial external shoulder on shell 46 and the annular end face of female shell 33.

Although only a limited number of embodiments of the invention are herein illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto For example, it will be apparent vthat the cable or plug portion 11, 23 of the embodiment of FIG. l may be coupled with the jack or socket contact portion of FIG. 2. Likewise, the plug or pin contact portion of FIG. 2 may be coupled to the socket contact portion 5 of FIG. 1. Various changes may also be made, particularly in the detail design and arrangement of the parts illustrated, without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art.

What is claimed is:

1. The combination comprising a coaxial cable having its inner conductor exposed beyond the end of its outer conductor and the end of the cable insulation between said conductors, said inner conductor including the exposed portion thereof having a substantially uniform outer diameter and said outer conductor having a substantially uniform inside diameter, a tubular metallic casing, tubular insulating means disposed within said casing and securely captured between spaced internal shoulders in the casing, the shoulder at one end of the insulating means being constituted by the inner transverse face of an annular internal flange in the casing, said insulating means having a reduced end portion extending through said flange and terminating flush with the outer transverse face thereof and a stepped bore, the smaller diameter portion of which extends through said reduced end portion and slidably receives said exposed portion of the inner conductor, the diameter of the internall surface of said flange being substantially equal to the inner diameter of said outer conduct-or, a socket contact having a close fit within the larger diameter portion of said bore for receiving the exposed end of said inner conductor of the cable and positioned axially by the step between said larger and smaller bore portions, a tubular metallic member closely surrounding and secured to the end portion of the outer conductor of said cable and having a portion slidably telescopically received in one end of the casing, an end of said member being flush with the end of the outer conductor, and means for holding the tubular member in telescopic coaxial relation with the casing with the ends of said member and outer conductor in electrically conductive engagement with the outer transverse face of said flange.

2. The combination as defined in claim 1, wherein said holding means comprises a nut coopera-ble with said casing and tubular member, said member having an annular external shoulder in face-to-face relation with van annular end surface of the casing and further comprising a yieldable gasket under compression between said external shoulder and said end surface when said tubular member engages said flange.

3. The combination as defined in claim 1, wherein the contact positioning step in the bore of said insulating means is in a transverse plane spaced a short distance inwardly from the plane of said inner transverse face of the flange, said distance being predetermined to electrically compensate for the variations in the characteristic impedance of the coaxial line which would otherwise result from the difference in the diameters of the inner surfaces of the connected outer conductor and casing and in the diameters of the outer surfaces of the connected inner conductor and socket contact of the aforesaid assembled parts.

4. In a connector for coaxial cables, a tubular metallic casing constituting an outer conductor and having an internal shoulder and an internal annular flange, the inner diameter of the casing being uniform between said shoulder and flange, tubular insulating means captured between said shoulder and the inner transverse `face of said flange and having a stepped bore, said insulating means also having a reduced portion at one end thereof with the smaller bore portion therethrough, said reduced portion extending through said flange and terminating flush with the outer transverse face thereof, and a socket contact constituting an inner conductor within the larger bore portion of the insulating means and axially positioned therein by having the pin receiving end thereof abutting the step between said smaller and larger bore portions, said socket contact being adapted to receive a pin contact slidably projecting through said smaller bore portion of the insulating means into the socket contact and constituting a reduced diameter extension of the inner conductor, said socket contact positioning step in said insulating means being in a transverse plane spaced inwardly from the plane of said inner transverse face of the flange a short distance calculated to compensate for electrical disturbances which would result from the steps in said inner and outer conductors at said planes.

5. The combination as defined in claim 4 further comprsing a coaxial cable having its inner conductor exposed beyond the end of its outer conductor and the end of the cable insulating therebetween to form said pin contact for receipt by said socket contact, a metallic ferrule surrounding and secured to the outer conductor of the cable, said ferrule terminating flush with the end of said outer conductor of the cable and having a portion slidably telescopically received in the end of said casing, and a coupling member cooperatively associated with said casing and ferrule for lholding the ferrule and cable in telescopic relation with the casing with the ends of said insulating means and said cable insulation in abutting relation.

6. A connector for coaxial cables comprising a tubular metallic casing having a central bore portion of uniform diameter, an internal flange at each end of said bore portion and an enlarged counterbore at each end, at least one of said flanges being constituted by a metallic ring secured in the inner end of the counterbore at one end of the casing, tubular insulating means captured between said flanges and having reduced end portions closely surrounded by said flanges, the bore through said insulating means having a central portion of uniform diameter and reduced diameter portions through said reduced end portions, and a double-ended socket contact axially coextensive with and captured between annular shoulders at the ends of the central enlarged portion of the bore in said insulating means, the inner diameters of the sockets in said contact being of approximately the same diameter as the diameter of the reduced portions of the bore in said insulating means.

7. A connector as defined in claim 6, wherein said reduced portions of the bore through said insulating means extend inwardly a predetermined short distance beyond the inner ends of said reduced end portions of the insulating means, said distance being calculated to electrically compensate for variations in the characteristic impedance of the coaxial line which would otherwise result from the difference in diameters of the inner surfaces of the central bore portion of the casing and a said flange and the difference in the diameters of the outer surfaces of said socket contact and a pin contact adapted to slidably extend through said reduced diameter bore portion and into said socket contact.

8. The combination comprising a coaxial cable having a braided metallic wire outer conductor, the inner conductor of said cable being exposed beyond the end of the cable insulation between the conductors and the cable insulation being exposed beyond the end of the outer conductor, a tubular metallic shell comprising a first section at one end having a uniform first bore for slidably receiving the insulated inner conductor of said cable, said first section being externally tapered to be received within the expansible outer conductor of said cable, a second section intermediate the ends having Ia uniform second bore of greater diameter than said first bore and a third section at the other end having a uniform third bore of greater diameter than said second bore, a metallic ring secured in said third bore at the end thereof adjacent said second bore, said ring having a lesser internal diameter than said second bore, tubular insulating means 7 filling the second bore and the bore through said ring, the passage through said insulating means being stepped and the smaller diameter portion thereof being surrounded by said ring, and a socket contact'axially positioned at one end in the larger diameter portion of said passage by the step therein and being adapted to be secured at the other end to the exposed end of the inner conductor of said cable, the inner end of the smaller diameter portion of said passage through the insulating means terminating at a transverse plane spaced a predetermined distance inwardly rom the plane of the inner transverse face of said ring.

References Cited by the Examiner UNITED STATESv PATENTS EDWARD C. ALLEN, Primary Examiner.

W. DONALD MILLER, Examiner. 

1. THE COMBINATION COMPRISING A COAXIAL CABLE HAVING ITS INNER CONDUCTOR EXPOSED BEYOND THE END OF ITS OUTER CONDUCTOR AND THE END OF THE CABLE INSULATION BETWEEN SAID CONDUCTORS, SAID INNER CONDUCTOR INCLUDING THE EXPOSED PORTION THEREOF HAVING A SUBSTANTIALLY UNIFORM OUTER DIAMETER AND SAID OUTER CONDUCTOR HAVING A SUBSTANTIALLY UNIFORM INSIDE DIAMETER, A TUBULAR METALLIC CASING, TUBULAR INSULATING MEANS DISPOSED WITHIN SAID CASING AND SECURELY CAPTURED BETWEEN SPACED INTERNAL SHOULDERS IN THE CASING, THE SHOULDER AT ONE END OF THE INSULATING MEANS BEING CONSTITUTED BY THE INNER TRANSVERSE FACE OF AN ANNULAR INTERNAL FLANGE IN THE CASING, SAID INSULATING MEANS HAVING A REDUCED END PORTION EXTENDING THROUGH SAID FLANGE AND TERMINATING FLUSH WITH THE OUTER TRANSVERSE FACE THEREOF AND A STEPPED BORE, THE SMALLER DIAMETER PORTION OF WHICH EXTENDS THROUGH SAID REDUCED END PORTION AND SLIDABLY RECEIVED SAID EXPOSED PORTION OF THE INNER CONDUCTOR, THE DIAMETER OF THE INTERNAL SURFACE OF SAID FLANGE BEING SUBSTANTIALLY EQUAL TO THE INNER DIAMETER OF SAID OUTER CONDUCTOR, A SOCKET CONTACT HAVING A CLOSE FIT WITHIN THE LARGER DIAMETER PORTION OF SAID BORE FOR RECEIVING THE EXPOSED END OF SAID INNER CONDUCTOR OF THE CABLE AND POSITIONED AXIALLY BY THE STEP BETWEEN SAID LARGER AND SMALLER BORE PORTIONS, A TUBULAR METALLIC MEMBER CLOSELY SURROUNDING AND SECURED TO THE END PORTION OF THE OUTER CONDUCTOR OF SAID CABLE AND HAVING A PORTION SLIDABLY TELESCOPICALLY RECEIVED IN ONE END OF THE CASING, AN END OF SAID MEMBER BEING FLUSH WITH THE END OF THE OUTER CONDUCTOR, AND MEANS FOR HOLDING THE TUBULAR MEMBER IN TELESCOPIC COAXIAL RELATION WITH THE CASING WITH THE ENDS OF SAID MEMBER AND OUTER CONDUCTOR IN ELECTRICALLY CONDUCTIVE ENGAGEMENT WITH THE OUTER TRANSVERSE FACE OF SAID FLANGE. 